The present invention relates to a master cylinder comprising a cylindrical body pointing along a main axis and having a free end, an attached end, and a piston rod projecting axially from the attached end.
In practice, all the master cylinders used in hydraulic braking systems for motor vehicles ever since the latter were invented correspond to this definition.
However, a tightening of safety standards has revealed a need to develop master cylinders in such a way that a frontal impact applied to the vehicle cannot be readily transmitted to the driver's leg by the master cylinder, even if the impact occurs while the driver is putting all of his weight on the brake pedal.
In order to achieve this, it is known practice, at least in some recent embodiments, for the master cylinder locally to be given a shape by virtue of which it can retract laterally when it receives an axial impact from a part of the engine which has been displaced by a frontal impact of the vehicle.
Such a solution does, however, have two major drawbacks.
On the one hand, insofar as the internal layout of the engine bay of a vehicle is practically specific to each vehicle, and as the most dangerous angle of impact on the master cylinder therefore varies from one vehicle to another, the known solution requires a master cylinder to be designed for each vehicle, and this leads to absolutely prohibitive development and manufacturing lead times and costs.
On the other hand, insofar as a master cylinder has to be manufactured from a metal which has physical properties which suit the conditions of manufacture, leaktightness and reliability with which a master cylinder has to comply, any excess of this metal with a view to fulfilling an impact-deflector function leads both to a substantial on-cost and to a risk of degrading the inherent performance of the master cylinder.